I bought / rented a 100% opt-in list from a reputable list broker

No: No matter what the list broker claims, you cannot use any kind of third party list with this software. There is no situation where it would be allowed, and it does not matter if you didn't have to pay for it – it still does not count as permission in this context.

That goes for industry-specific lists, too. For example, Adbase for photographers. A purchased list is a purchased list.

Everyone signed up through a mailing in my store / via my store website

Yes: Perfect! That's clear, direct permission. Just make sure you: only send them what you promised you would; don't wait months to email people for the first time; don't wait months between sending emails.

It is very common for people to forget about mailing lists they joined. That's why it's important to stay on target with the content you're sending and be consistent with the regularity of your emails.

We sponsored a trade show and got a list of everyone who attended

No: This is very common, but it does not count as permission. The people on those lists may have agreed to hear from every vendor as part of their entry, but it is not explicit, direct permission for your company to start emailing them.

Trade show and conference attendee lists are not allowed to be used with this software, even if the event organizer tells you it is fine.

We sponsored a trade show and people signed up at our booth to get our newsletter

Yes: Much better! Those people know who you are, and have specifically shown their interest in hearing from you.

Don't wait too long after the event to email them, and make sure to mention their visit to your booth in the first email.

This mailing list is a few years old, everyone signed up through my website / at my booth / in my store

Maybe: Permission is like bread, it starts out great but goes stale quickly. If you haven't emailed these people in the last year or so, they have probably forgotten about you, or may not be interested anymore.

If it's been between six months and a year since you last contacted them, you should start with a simple reminder email, asking them to unsubscribe if they are no longer interested.

These are all paying customers from my store / website

Maybe: That's a good start. If they are current or recent customers, meaning they have purchased within the last two years, you are safe to assume an existing relationship.

If it's been longer than two years, and you have not been emailing them regularly, then it is a no go zone. Permission does not last forever – use it or lose it.

These are all paying customers from my poker site / adult site / pharmaceutical site

No: Unfortunately you cannot. Our deliverability and sender reputation are maintained, in part, by not allowing the sending of gambling, adult or pharmaceutical emails at all – even from totally legitimate businesses.

They all bought something from my eBay store

No: This is a special case because, although they are your customers, eBay shoppers do not expect to get email from the people they buy from. The permission shoppers have granted in regard to sharing their email address is strictly linked to transaction purposes.

So unless your eBay customers sign up directly for your newsletter, their email address cannot be used in this system.

They registered on my site or forum and agreed to the privacy policy / terms of use

Maybe: That's good, but it isn't explicit opt-in. If they ticked an empty checkbox explicitly stating that they agree to receive your newsletter, then go for it.

However, hiding a line in your terms and conditions or privacy policy about receiving email, and making people agree to that is not considered opting-in.

We all know that most people never read those documents, so put the opt-in right on the sign up page instead, or you do not truly have their permission.

We're an employment agency and these are all of our candidates / employers

Maybe: You can send email to your own customers, meaning the people who have employed your agency's recruitment service, but there is a distinct difference between your customer and the job candidates.

You must receive a candidate's direct permission; a clear opt-in either verbally or electronically. A reference to newsletters in their contract or included in the terms of your site does not equal permission to send.

They are in the member directory of my local business chamber / real estate organization / sports association

No: Even when the organization itself says that people listed in the directory can be emailed, this does not qualify as a direct opt-in and the email addresses cannot be used in this software.

If you have talked to individuals in the member directory, and they have given you their direct permission, then you can add them to a mailing list.

We ran a competition and these are all the people who entered

Maybe: Be very careful with this one. Competition lists like this often cause spam complaints. If people give you their email address just to win a prize, the only thing you can email them about is the competition, to let them know who won the prize.

You don't have permission to send marketing content to them on any other topic. Hiding a sentence along the lines of 'you agree to be emailed forever' in 8pt font in the terms and conditions does not count as permission.

It is different if you promote the opportunity to win a prize by signing up to the newsletter. Then people know they will be emailed – and will be expecting to be able to unsubscribe easily if they don't like what you're sending them.

I just started a new company, I'm emailing all the customers of my current company

Maybe: In most cases this is not okay. Permission isn't permanent or flexible. Those people gave you permission in a particular context, relating to the company you worked for at the time and its product or service. They did not sign up to hear about other companies, even if you are involved in them.

These people all contacted me through my website

No: Sending in a question or comment isn't the same thing as opt-in permission. Even if your website form says "send me more information" it does not mean you can add them to a mailing list. It means you can send them specific information as requested.

Unless your contact form clearly displays the option to opt-in for a mailing list, and people do opt-in, you do not have permission.

These are all my friends / colleagues / family members

Maybe: That's nice, but unfortunately it doesn't give you permission to email them without an agreed opt-in from them. This could be as simple as asking them if it's okay to add them to your list.

We know they probably won't mind even if you don't ask, but that is not the same thing as opt-in, and is still not allowed.

They are all group members / followers / fans from LinkedIn / Facebook

No: That's an indication of interest, for sure, but it is not direct opt-in. They might want to have some connection to you but you cannot assume they want to be on your email list unless they actually ask.